The patient went on to have surgery.
Histology
MICROSCOPIC DESCRIPTION: The sections show a malignant pleomorphic tumour. The tumour forms nests and cords. No glandular structures are seen. No anastomosing vascular channels are noted. The tumour cells are mainly epithelioid in appearance with enlarged pleomorphic nuclei, prominent nucleoli and scanty ill-defined cytoplasm. Some cells have intranuclear pseudoinclusions. No brown cytoplasmic pigment is seen. Mitoses are inconspicuous. There is no evidence of lymphovascular invasion. Occasional eosinophils are noted in the background.
The tumour cells show positive staining for CD31 (histiocytic and vascular marker) and CD99 with some possible faint CD10 reactivity. There is patchy granular cytoplasmic staining for melan-A, of uncertain significance. All other melanocytic markers are negative (S-100, SOX-10, HMB-45, Tyrosinase). The Ki-67 index is about 20%. CAM5.2, AE1/3, CK7, CK20, CDX-2, TTF-1, p40, calretinin, CD34, c-kit, desmin, actin, myogenin, CD3, CD15, CD20, CD30, CD43, CD68 and ALK-1 are also negative. Carcinoma, melanoma and lymphoma have been excluded. The features are consistent with undifferentiated pleomorphic sarcoma, as a diagnosis of exclusion.
FINAL DIAGNOSIS: Undifferentiated pleomorphic sarcoma.